FROM ARTIFICIAL LIFE TO REAL LIFE: COMPUTER SIMULATION OF PLANT GROWTH∗

Artificial life is by itself an important area of scientific investigation. However, this scientific discipline will be more effective if it can also help one to understand how natural living systems really work. It is argued that plant growth is an area where the studies in artificial life lend themselves to computer modeling of what really happens in nature. An approach for such modeling is described, and the initial results of implementing this approach for a corn plant growth are presented.     

Performance improvement using time delays in multivariable controller design

A new controller for linear multivariable ordinary systems is suggested in which distributed delays are included in the feedback loop. A general design approach to obtain this type of controller is suggested. It is shown that the resulting closed-loop system is asymptotically stable under some sufficient conditions. Sufficient conditions are derived under which the disturbance attenuation, the robustness against parameter variations, and the time-delay stability margins are improved by the proposed controller. The state feedback tracking controller and the dual-state observer are obtained by modification of the proposed controller.     

Efficiency enhancement of dye-sensitized solar cells with addition of additives (single/binary) to ionic liquid electrolyte

The effect of addition of single and binary additives on the performance of dye-sensitized TiO₂ solar cells based on electrolytes containing an ionic liquid (IL), 1,2-dimethyl-3-propylimidazolium iodide (DMPII) has been studied. Among the seven additives used, the addition of 2-(dimethylamino)-pyridine (DMAP) to IL resulted in best cell efficiency, which showed further enhancement with the addition of 5-chloro-1-ethyl-2-methylimidazole (CEMI) as second additive. The efficiency of the dye-sensitized solar cell (DSC) based on an electrolyte containing binary additives (DMAP and CEMI in equal molar ratios) has been found to increase by 62·5% from 4·35 to 7·07%. The dependence of different photovoltaic performance parameters (V _oc, J _sc, ff, η) of DSC upon temperature has been studied over a 30–120°C range and only a small decrease in conversion efficiency has been observed. The electrolyte containing binary additives (DMAP and CEMI) shows best cell performance up to 120°C.     

Electrical Properties of Sputter-deposited ZrO2-based Pt/ZrO2/Si Capacitors

Pt/ZrO2/Si sandwich structures where ZrO2 is deposited by radio frequency （r.f.） magnetron sputtering using a Zr target in an atmosphere of O2/Ar gas mixture, were fabricated and the effects of the O2/Ar flow ratio in the reactive sputtering process, the annealing temperature, the ZrO2 film thickness on the structure, the surface roughness of ZrO2 films and the electric properties of Pt/ZrO2/Si metal-oxide-semiconductor （MOS） capacitors were investigated. The optimum process parameters of the Pt/ZrO2/Si capacitor based on reactively sputtered-ZrO2 determined in such a way as the capacitance is maximized and the leakage current, the oxide charge, and the interface trap density are minimized that is the O2/Ar flow ratio of 1.5, the annealing temperature of 800℃, and the film thickness of 10 nm. Also the conduction mechanism in the Pt/ZrO2/Si capacitor has been discussed.     

Numerical modelling of a low power non-transferred arc plasma reactor for methane conversion

Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane, which is the main component of shale gas, were simulated. The temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MHD) code and a commercial ANSYS-FLUENT code; the transport of chemical species was analyzed as including the chemical reactions of methane conversion. The simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%. Three C₂ hydrocarbon gases with ethane (C₂H₆), ethylene (C₂H₄), and acetylene (C₂H₂) were selected as the converted species of methane from experimental data. The mass fraction of C₂ hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also calculated. Those values show good agreement with the actual experimental results in that the major conversion reaction occurred in C₂H₂ and hydrogen, and the conversions to C₂H₆, C₂H₄, and hydrogen were minor reactions of methane pyrolysis conversion.     

TOXICITY, MUTAGENICITY AND TERATOGENICITY OF BREVIANAMIDE, VIOMELLEIN AND XANTHOMEGNIN; SECONDARY METABOLITES OF PENICILLIUM VIRIDICATUM

The three major secondary metabolites of Penicillium viridicatum, brevianamide, xanthomegnin, and viomellein were tested for mutagenicity by the Salmonella/microsome test and for toxicity and teratogenicity by the chick embryo test. None were mutagenic. Viomellein was mildly toxic and teratogenic, xanthomegnin was the most toxic and was not a teratogen, and brevianamide was not toxic yet was the most teratogenic.     

Effects of Post-Harvest Handling and Processing on Vitamin Contents of Peas

Vitamin contents of peas were measured at various stages of raw product handling, during 1976–1979 seasons, on different cultivars, on different sizes of peas, at various stages of processing, and at different processing plants. Some cultivar differences were shown in ascorbic acid, carotene, and folic acid, and different sizes of peas contained significantly different amounts of ascorbic acid, carotene, and thiamin contents. Profound effects were observed during blanching and thermal processing of peas. Ascorbic acid, thiamin, vitamin B₆, and niacin contents of canned peas were significantly (95% level) lower than those of fresh peas. Also some significant differences in vitamin contents of canned peas among different processing plants were observed.     

Relation between etching profile and voltage–current shape of sintered SiC etching by atmospheric pressure plasma

Sintered silicon carbide (SiC) was etched by a dielectric barrier discharge source. A high voltage bipolar pulse was used with helium gas for the plasma generation. One stable filament plasma was generated and could be used for SiC etching. As the processing gas (NF₃) mixing rate increased, the width and depth of the etching profile became narrower and deeper. The differentiated V–Q Lissajous method was used for measuring the capacitances (C_eq) of the electrode after the plasma turned on. The width of the etching profile was proportional to C_eq. As the current peak value I_smx of the substrate current increased, the volume removal rate of SiC increased. The etch depth was proportional to the ratio of I_smx to C_eq. Additionally, because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity, the etching profile was unstable. However, in high NF₃ mixing process, the etching profile became stable and deeper.     

Computational study on influence of RF shielding box on inductance of coil

Despite the fact that a radio frequency (RF) shielding box affects a coil inductance used in matching network, RF engineers have used a coil inductance measured in open space on designing matching networks since it is difficult to precisely measure the coil inductance within the RF shielding box. In this work, we investigate the influences of the RF shielding box on the coil inductance via a 3D full electromagnetic wave simulation. Simulation results shows that the coil inductance decreases from -6.0% to -11.9% compared with its ideal inductance depending on coil positions within the RF shielding box. Both inductive and capacitive coupling between the coil and surfaces of the RF shielding box contribute to the reduction of the coil inductance. We expect that these results would be useful for those who design RF matching networks.